Xystos (Greek ξυστός ) called by the Greeks the covered raceway, which was, in the Greek gymnasium next to the dromos or Peridromides ( περιδρόμιδες ) sometimes the entire gymnasium.

Among the Romans the Xystus Vitruvius was a portico, ran beside the not covered, plane trees lined roads that identifies Vitruvius with the Peridromides, but Xysti calls.

Finally, the Xystus was as an avenue essential part of Roman gardens, where it is generally parallel to a colonnade ( portico or cryptoporticus ). In the sources, these walks are often witnessed, but archaeological rarely shown due to their nature, for example in the Villa Romana del Casale.